SEATTLE, March 18 (Reuters) - A news helicopter crashed and burst into flames in downtown Seattle near the Space Needle on Tuesday, killing a pilot and a photographer on board and setting three cars on fire in the popular tourist area, officials said.

The chopper appeared to have fallen to the street as it attempted to take off from a helipad at the top of a television news station, Seattle Fire Department spokesman Kyle Moore told reporters. Witnesses reported an "unusual noise" coming from the helicopter during its departure.

Two people were found dead in the wreckage of the helicopter when emergency responders arrived at the scene, while the occupants of three vehicles that caught fire managed to escape, Moore said. One person was in critical condition.

Television station KOMO, an ABC affiliate, said the aircraft was one of its helicopters. Photos posted online by the station showed flames and smoke rising from cars at the scene after the crash.

"I saw it falling. It was coming down head first," said Carmen Romero, who had been walking to catch a bus when the crash happened. "It hit the car. Then flames went up."

Romero said she saw a man engulfed in flames emerge from one of the three vehicles, waving his arms as he ran.

The morning crash, which left burning helicopter fuel streaming down the road and debris strewn on grass at the base of the Space Needle, occurred in a tourist area that also hosts a children's museum and the Pacific Science Center. The weather was overcast at the time, with little wind.

After the fire was extinguished, the charred vehicles with their windows blown out remained in the street, which was covered in fire-retardant foam. The tail of the chopper was several yards from its main frame.

The two people killed were pilot 59-year-old Gary Pfitzner, who worked for a company that operated the helicopter for the TV station, and photographer Bill Strothman, 62, who shot video for KOMO but had retired from the company and worked as a freelancer, according to KOMO.

"At times like this we are reminded that the media, like many of us, are also public servants," said Seattle Mayor Ed Murray, who visited Strothman's adult children after their father's death.

U.S. Senator Maria Cantwell, a Democrat from Washington state, said in a statement that the crash was "an unimaginable loss for Seattle's journalism community."

SERIOUS BURNS

Of the people who were in the vehicles that burned in the crash, a man in his late 30s who escaped his car was hospitalized.

The fire department said he was initially listed in critical condition, but a hospital spokeswoman later said he had been upgraded to serious condition with burns over 20 percent of his body.

A woman who escaped a second car that burned after the crash had made her way to a police station and appeared to be in good shape, and the driver of a pickup truck scorched at the scene walked away unharmed, officials said.

City officials will review regulations for helipads, the mayor said.

The Space Needle and the Seattle Monorail, which runs near the crash scene and connects a downtown shopping mall to the Seattle Center tourist complex, were shut down to prevent people from looking down at the bodies, Murray said.

The National Transportation Safety Board, whose investigators were at the scene, planned to clear the wreckage by Tuesday evening and issue a preliminary report in five days, said Dennis Hogenson, acting deputy NTSB chief for the western Pacific region.

Witnesses reported hearing an "unusual noise" coming from the helicopter during its departure, with one person saying the engine sounded as if it were "whining," and investigators were looking into whether the main rotor may have clipped the tail, Hogenson said.

"We're looking at the environment, the weather, the pilot, the operators in the helicopter, as well as the helicopter itself, as well as the background of all of the above," he said.

The helicopter, a 2003 Eurocopter AS350, appeared to have rotated counterclockwise before it crashed, he said. He added that the helicopter had been flown on Tuesday morning and was brought back to the downtown area to refuel.

After less than 30 minutes on the helipad, the pilot attempted the ill-fated takeoff, Hogenson said. (Additional reporting by Eric M. Johnson in Seattle, Jonathan Kaminsky in Olympia, Wash.; Writing by Alex Dobuzinskis; Editing by Cynthia Johnston, Mohammad Zargham and Amanda Kwan)